Experimental characterization of the dynamic failure resistance of TiB2/Al2O3 composites

The dynamic compressive strength and microscopic failure behavior of TiB2/Al2O3 ceramic composites with a range of microstructural morphologies and size scales are analyzed. A split Hopkinson pressure bar (SHPB) is used to achieve loading rates of the order of 400 s-1. The dynamic compressive strength of the materials is found to be between 4.3 and 5.3 GPa, indicating a strong dependence of strength on microstructure. Microstructures with finer phases as measured by linear intercept length have higher strength levels. The dynamic strength levels are approximately 27% higher than the values of 3-4 GPa measured at quasi-static loading rates for these materials. These strength levels are also higher than the strength levels of monolithic TiB2 and Al2O3 under similar dynamic conditions. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) indicate that failure associated with the Al2O3 phase is transgranular cleavage in all microstructures and failure associated with the TiB2 phase is a combination of transgranular cleavage and intergranular debonding and varies with the microstructures. The measured compressive strength of the materials directly correlates with the fraction of TiB2-rich areas on fracture surfaces